Field-grown terrestrial vegetation, such as plants grown in orchards and arbors, as well as other woody and herbaceous plants, is managed today in a manner that has changed little over the past several centuries. This is primarily due to the management requirements of the naturally distributed root system, which tends to be horizontal and near the soil surface (i.e., primarily in the top 2 to 4 feet of the soil profile), which is shown in FIG. 1. Horizontal root distribution requires that much care and management go into ensuring the uniform distribution of water, chemicals and nutrients so that all of a plant's root system can benefit. Even with the advent of sprinkler irrigation and chemical sprays, the horizontal root distribution pattern of woody plants requires large areas for development and, along with top growth, helps dictate plant population density.
Plant establishment and growth can be affected by root zone management. Weeds and other vegetation competing for water and nutrient inputs is one of the critical obstacles to plant establishment and growth after planting. Considerable cost and effort is provided to overcome the negative impact of this competition. Failure to limit this competition typically results in poor establishment and growth of a plant.
Crop production, both quality and quantity can also be affected by root zone management. For example, in citrus trees, only the outer 3-foot layer of the canopy is productive. Of the inner layer, productivity is limited by the shading of the outer layer. As a result, trees with larger diameter canopies take up more space but are less productive on a per unit area basis. In recent years, researchers have been exploring methods to increase plant populations of citrus groves. One method is to plant more trees and aggressively prune the top growth of the tree to prevent the canopies from developing large diameters. Other methods have studied root pruning by physical and chemical means to help limit the canopy diameter. Again, the primary reason for trying to limit the canopy diameter and increase plant populations in these situations is to increase crop productivity.
Management and production of arbors, such as grapes, can also be difficult for a number of reasons. Heavy rainfall at inopportune times, such as during the critical pre-harvest period, can cause the fruit to become gorged with water and split, potentially spoiling much of the value of the crop. In addition, much attention has been directed to the spreading of soil-born diseases such as Armillaria mellea throughout vineyards up and down the California coastline. At the same time, this multi-billion dollar industry is under increasing pressure ranging from the ban on soil fumigants, growing competition for water and the need to limit pollution. For example, the ban of the soil fumigant methyl bromide in 2005 is anticipated to have severe economic implications for growers, and the demand for an alternative product or method is great.
Another limitation to productivity caused by a naturally developed horizontal root system is the common need to allow the land to lie fallow for a period of time after the removal of dead or diseased trees and before replanting new trees can occur. This is primarily caused by the necessity to either eliminate pathogens in the soil or reduce the phytotoxic effects on the new root system by the old root system. As a result, land may be unproductive for up to five years and may require significant management during that same period.
Beyond productivity, environmental pollution caused by the runoff and leaching of chemicals and nutrients into the groundwater is also of major concern in some areas. Even with tightly controlled irrigation programs that would limit the potential for chemical leaching, uncontrolled rainfall events can flush chemicals out of the root zone, through the soil profile, and into the groundwater, potentially allowing the chemicals to be washed or eroded from the soil surface into public waterways.
These and other issues associated with the management of horizontal root systems can be mitigated through the application of deep rooting technology. This technology can be utilized to develop columnar-like root distribution where inputs such as irrigation, chemicals and nutrients can be tightly controlled.